Abstract
BackgroundThe production of agricultural wastes still growing as a consequence of the population growing. However, the majority of these residues are under-utilized due their chemical composition, which is mainly composed by cellulose. Actually, the search of cellulases with high efficiency to degrade this carbohydrate remains as the challenge. In the present experiment, two genes encoding an endoglucanase (EC 3.2.1.4) and β-glucosidase (EC 3.2.1.21) were overexpressed in Escherichia coli and their recombinant enzymes (egl-FZYE and cel-FZYE, respectively) characterized. Those genes were found in Trabulsiella odontermitis which was isolated from the gut of termite Heterotermes sp. Additionally, the capability to release sugars from agricultural wastes was evaluated in both enzymes, alone and in combination.ResultsThe results have shown that optimal pH was 6.0 and 6.5, reaching an activity of 1051.65 ± 47.78 and 607.80 ± 10.19 U/mg at 39 °C, for egl-FZYE and cel-FZYE, respectively. The Km and Vmax for egl-FZYE using CMC as substrate were 11.25 mg/mL and 3921.57 U/mg, respectively, whereas using Avicel were 15.39 mg/mL and 2314.81 U/mg, respectively. The Km and Vmax for cel-FZYE using Avicel as substrate were 11.49 mg/mL and 2105.26 U/mg, respectively, whereas using CMC the enzyme did not had activity. Both enzymes had effect on agricultural wastes, and their effect was improved when they were combined reaching an activity of 955.1 ± 116.1, 4016.8 ± 332 and 1124.2 ± 241 U/mg on corn stover, sorghum stover and pine sawdust, respectively.ConclusionsBoth enzymes were capable of degrading agricultural wastes, and their effectiveness was improved up to 60% of glucose released when combined. In summary, the results of the study demonstrate that the recombinant enzymes exhibit characteristics that indicate their value as potential feed additives and that the enzymes could be used to enhance the degradation of cellulose in the poor-quality forage generally used in ruminant feedstuffs.
Highlights
The production of agricultural wastes still growing as a consequence of the population growing
Cellulose digestion is achieved using enzymatic complexes that include different enzymes that work synergistically, and the widely accepted mechanism underlying the enzymatic hydrolysis of cellulose involves three types of enzymes, namely endoglucanases, which randomly hydrolyze β1,4 linkages, cellobiohydrolases, which break down cellobiose units from nonreducing ends, and β-glucosidases (EC 3.2.1.21), which break down glycosyl group from the non-reducing ends of cello-oligosaccharides [7]
Protein mass In the present study, two genes were cloned from T. odontotermitis, and their expressed products, which exhibited endoglucanase and a βglucosidase activity, respectively, were selected based on previous annotation of the T. odontotermitis genome [21]
Summary
The production of agricultural wastes still growing as a consequence of the population growing. Two genes encoding an endoglucanase (EC 3.2.1.4) and β-glucosidase (EC 3.2.1.21) were overexpressed in Escherichia coli and their recombinant enzymes (egl-FZYE and cel-FZYE, respectively) characterized Those genes were found in Trabulsiella odontermitis which was isolated from the gut of termite Heterotermes sp. More than 1.5 billion metric tons of agricultural residues were produced in the 1990s alone [1], and Mexico currently produces around 45 million tons per year, according to the government [2] Most of these residues remain under-utilized, owing to their chemical composition (mainly cellulose, hemicellulose, and lignin) [3], and, they are burned, representing a potential environmental risk [4]. Some insects (e.g., termites) have been reported to produce endogenous cellulases that enhance the digestion of cellulose by symbiotic microbes [9]
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